update create groups endpoint - fixing errors when adding students to the group

backend/app/coordinator/routes/groups.py

@@ -60,13 +60,13 @@ def create_group(data: dict) -> dict:
     if students_without_groups != len(students_indexes):
         abort(400, "One or more students have already belonged to group!")
 
+    db.session.add(group)
+    db.session.commit()
+
     students = db.session.query(Student).filter(Student.index.in_(students_indexes)).all()
-    project_supervisor.count_groups += 1
     for student in students:
         student.group_id = group.id
 
-    db.session.add_all(students)
-    db.session.add(group)
     db.session.commit()
 
     return {"message": "Project Supervisor was created!"}